Research On Random Access Technology Of Fdd-LTE Based On SDR

High-speed broadband data communication is the trend of the development of future wireless communications. Based on the consideration of future development, the Third Generation Partnership Project (3GPP) launched the "Long Term Evolution"(LTE) process. Based on the technologies of OFDM&MIMO, LTE which captures the attentions of various operators is characterized by high transmission rate, high spectral efficiency, resistance to multipath fading. At the same time, the applications of Software Defined Radio Technology (SDR) in the field of mobile communications has made remarkable progress in recent years. Huawei’s3G base stations based on SDR technology have entered the highly competitive WCDMA market of European, which is leading in the market. The application of SDR technology based on a general purpose processor (GPP) in LTE is becoming a hot spot nowdays.In LTE, the physical random access channel (PRACH), is mainly used for initial access requests from the user equipment (UE). In case of accessing to the LTE network, a UE launches access request by transmitting the random access preamble to eNodeB through PRACH. The PRACH preamble detector of the eNodeB is able to detect the presence of PRACH preamble, and estimate the exact ID of PRACH preamble in order to response correctly to the UE which requested initial access. Moreover, propagation delay between UE and eNodeB should be calculated by PRACH preamble detector due to the notification of timing advance (TA) information to UE.This paper focuses on the research of FDD-LTE random access technology. In the first place, we introduced the background, performance requirements, and key technologies in physical layer. Then the scenarios of random access technology, the access procedure, the design of PRACH signal and the flow in transmitting side of PRACH is described and analyzed in detail. Then, for receiving the PRACH signal, we analyzed how to receive and detect the random access preamble sequence. Based on the research of traditional random access detection algorithm, we proposed a new detection algorithms which has a high accuracy of TA estimation. In order to eliminate the impact of the new algorithm on detecting perfomance, we adopt a semi-dynamic detecting threshold. At last, according to the characteristics of the SDR system based on general-purpose processor and the previous analysis of PRACH, we completed the design and implementation of FDD-LTE PRACH link in the SDR system. In order to solve the immediate problem of the system, we took a series of measures to optimize the system, which greatly reduced the system processing delay.